In the prior art, the application of developer to wafers for the purpose of removing photoresist has been accomplished in principally two manners.
One of the common manners of developing or removing photoresist has been accomplished by spraying the photoresist onto one wafer at a time which is individually handled. The developer solution which is sprayed onto the single wafer carries away the photoresist which is removed and then the developer solution with the small quantity of photoresist is put down the waste drain and is forever lost.
Another principal method of applying the developer to such wafers is to provide a tank of developer solution in which the silicon base wafers are dipped so that the photoresist is removed in the tankful of developer solution. After the tankful of developer solution has been used with a certain number of wafers for the purpose of removing the photoresist, the entire tank of developer solution is simply dumped down the waste drain, and the tank is again filled with fresh solution and the dipping process again commences and continues.
In this dipping process of removing photoresist, the small quantities of photoresist removed from the wafers is accumulated in the developer solution and over a period of time, the quantities of photoresist build up to a significant level.
As the quantities of photoresist increase in the developer solution, the cycle time for each successive wafer or batch of wafers must be progressively increased because the developing capabilities of the developing solution are progressively decreased.
Typical of the photoresist used on the wafers are those manufactured and sold by Hunt Chemical Company, Palisades Park, New Jersey, and known as Hunts LSI Type II; and those manufactured and sold by Shipley Chemical Company of Newton, Massachusetts, and known as Shipley 1350 B, Shipley 1350 J, and Shipley 1370.
Typical of the developing solutions which are commonly used for removal of such photoresist are sold by said Hunt Chemical Company, known as Hunts LSI Type II; and are sold by said Shipley Chemical Company and known as Shipley AZ 350.